1. Field of the Invention
The present invention relates to an optical lens system, and more particularly to a three-piece optical lens system.
2. Description of the Prior Art
In recent years, with the popularity of the mobile phone cameras, the optical lens system has become smaller in size, and the electronic sensor of a general digital camera is typically a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) sensor. Due to advances in semiconductor manufacturing, the pixel size of sensor has been reduced continuously, and miniaturized optical lens systems have increasingly higher resolution. Therefore, there's an increasing demand for an imaging lens system with better image quality.
Referring to FIG. 5, conventional miniaturized lens systems mostly consist of three lens elements, from the object side to the image side: a first lens element 91 with a positive refractive power, a second lens element 92 with a negative refractive power and a third lens element 93 with a positive refractive power. However, the third lens element 93 of the above patent is positive so that the principal point is close to the image side of the system, so the back focal length of such a three-piece lens assembly is relatively long, which results in a relatively large mechanical structure. As a result, the requirement of miniaturization can not be satisfied and the image quality of the periphery of the image will be reduced.
Therefore, the present invention is aimed at providing an optical lens system which can satisfy the requirement of miniaturization and improve the image quality of the periphery of the image.
The present invention mitigates and/or obviates the aforementioned disadvantages.